Page 185 - Math Course 1 (Book 1)

Proportions and Ratios

Describe Proportional Describe Proportional Relationships
Relationships MUSIC
Lindsay paid $10.89 to download an album with
Examples 11 songs. Write an equation relating cost to the
number of songs downloaded. How much would
an album of 13 songs cost?
WORK
Nina charges $5 for each day of pet sitting. Write A. The cost c is related to the number of songs s
an equation relating the cost of pet sitting to the by the equation c = 0.99s. An album of 13 songs
number of days. What would be the cost of pet would cost $12.87.
sitting for 4 days?
B. The cost c is related to the number of songs s
Find the constant of proportionality. by the equation c = 0.99s. An album of 13 songs
would cost $13.99.
Words $5 for each day of pet sitting
C. The cost c is related to the number of songs s
by the equation c = 1.01s. An album of 13 songs
would cost $13.13.
Variable Let d = number of days of pet
sitting and c = total amount Nina D. The cost c is related to the number of songs s
charges.
by the equation c = 1.01s. An album of 13 songs
Equation c = 5d would cost $12.12.

c = 5d Write the equation.
Answer
= 5(4) Replace d with the number of days.

= 20 Multiply.

Answer c = 5d; $20

Your Turn!

Identify Proportional Relationships
Determine whether the set of numbers in the table
are proportional. Explain your reasoning.

Passes Received 52 40 22 13
Number of Yards 689 596 289 221
Gained
1
A. Yes, all the rates are equal to
13.25
1
B. Yes, all the rates are equal to
14.9
C. Yes, all the rates are equal to 1
17
D. No, the rates are not equal.

Answer

177